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entran sra'rns rarnn'r orrrcn JOHN L. GILLILAND, OF NEW YORK, N. Y.

MANUFACTURE OF GLASS LENSES.

Specification of Letters Patent No. 9,184-, dated VAugust 10, 1852.

To all whom it may concern:

Be it known that I, JOHN L. GILLILAND, of New York, N. Y., have inventeda new and useful Manufacture of Molded and Pressed Dioptric Lenses, andthat the following is a full, clear, and exact description thereof,reference being had to the accompanying drawings, making part of thisspecification.

The dioptric lens heretofore and at the present time in use for sealights and for other lights requiring great intensity being constructedof single Zones or rings made up of segments according to the diameterof the required lens has induced a belief that glass could not beprepared without incurring the expense of grinding and pol-v ishing thecurved surface and that economy dictated a method of manufacturing,embracing a center and Zones or segments.

An examination into the necessity daily shown for the more general useof a dioptric lens to the purpose of a sea light including under thatname either revolving or stationary coast light, bay light, bar light,ship signal light, deck and between deck light, port light and all otherlight for ships, tide light, floating light and coast, harbor and riverlight, generally, and also a land light, including under that namerailway locomotive light, carriage light, ferry light, and as applied toarchitectural purposes, and in fact to any purpose where an intensity oflight is required, induced me to examine the :method of construction ofthe built-up lens and essay at least to reduce the expense withoutreducing the strength of the light.

Oommencing with the suggestions of Buffon that a spherical body from itsthickness absorbs lightin proportion to its density and that a sectionalfigure of any required shape and thickness could be cast of vitriiiedmaterial or glass and ground in steps or concentric zones to produce alens as executed with partial success by the Abb Rochon, from theexpense incident to the accuracy required in grinding and polishing thesteps or Zones; although I could fully appreciate the lens of Buffon itwas beyond the reach of the million by reason of the cost. Theexperiments of the Abb Rochon were, however, useful in preparing the wayfor the manufacture of the dioptric lens in separate pieces which wassubsequently accomplished by the ingenious Fresnel, after thesuggestions of Oondorect, known as the annular band lens at the presenttime in use in several light houses, in which the spherical aberrationsare nearly corrected by making the foci of each zone to coincide.

Although of great utility, the enormous expense of making the annularband lens of Fresnel, in which, not only must each separate piece haveits surfaces formed with great accuracy but all the several pieces mustbe fitted to each other so that when put together they shall constitutea perfect whole, has limited the use of this otherwise valuable anddesirable invention to a very few localities.

The object of my invention is to produce a dioptric lens which shallpresent all the practical advantages of the annular band lens of Fresneland at the same time so cheap as to admit of being applied to allpurposes requiring intensity of light, and to the end my inventionconsists in a new manufacture of dioptric lenses made in one or severalpieces molded and pressed, the form required for the surfaces, and (whenmade of several pieces) the required fit of the several parts beingproduced by giving the reversed required form to the metal molds inwhich the molten glass is to be put and into and by which it is to bepressed the pressure to be applied being sufficient to produce therequired surfaces and angles.

The mode of procedure which I have adopted with success is as follows,reference being had to t-he accompanying drawings and marked Nos. 1, 2and 3.

In the accompanying drawings No. 1, a, represents a circular mold toreceive the melted glass; b, is a follower which rests on the mold asshown at b, b2. c', is a plunger which fits into the follower Z), andwhich is intended to spread the melted glass uniformly into the mold a,by pressure; the mold, plunger and follower as described being wellknown to glass workers. rlhe mold may be made of any figure required andthe follower and plunger will be made to correspond with the mold. Themold a, instead of having the concentric central lens and rings asshown, may present a plane surface and the melted glass laid thereon andthe follower o, placed as hereinbefore described, the plunger c havingon it the rings and figures as shown in the mold a, by pressure upon themelted glass as already described will produce the required figure. Theshape ofthe mold may be changed to any figure whether convex or concavewith the central zones or rings. (Z, is a section of a, taken at thedotted lines e, f, and shows in section the gure of a lens.

The mold instead of being made of one piece as at c, a, may be madesectionally of as many separate rings or zones as there are designed tobe rings or zones in the lens or otherwise sectionally divided accordingto convenience, a suitable allowance in the diameter of each being madefor the increased aggregate diameter by reason of the parts beingdistinct, and in such cases the molds for the separate rings and zonesbeing laid together and securedl in their proper order, will form theentire mold while the interstices left between the separate pieces willanswer the same purpose as the holes in the angles of the zones,subsequently described, viz.: to suffer the air to escape when thepressure is applied.

If it should be desired (as it may be in the case of very large lights)to cast the lens itself in sections ,the several sections may be moldedand pressed as described above, and then the whole cemented together inthe usual way.

g, shows a concentric dioptric lens corresponding with the molds a, andis set in a frame ready for use. The frame may be made of any suitablemetal.

No. 2. 7L, shows three sides of a figure, of which i is a sectional viewtaken at z, 2, containing six sides, each lens having a convex centerand several sections of zones or rings. K shows a ligure made in threepieces 7c', 7a2, 7a3, which will require three separate molds or it maybe made in one mold. The six sided gure 7L, is illustrated to show thatit may be addedrto or diminished in the number of lens to be used. Theseveral lenses to make up the required ligure may be set in a metalframe; the cap Z, may be varied in shape and may be made of any suitablemetal.

No. 3, shows a dioptric cylinder m, applicable to the purposes of alantern containing several zones or rings with annular bands of regularand irregular widths which can be varied at pleasure and may bemanufactured of any length or circumference. n, shows a transversevertical section of m, as applied to the purposes of a hanging or handlantern with a stand lamp, top and ring attached.

If required, each lens may be made of one or many zones or concentricrings with the central lens according to the diameter the lens orsegment of a lens being produced as shown and described, by pressure, ina mold with or without fire polishing a process well known among glassworkers.

To promotefocal intensity and to prevent the absorption of light it willbe obvious that each lens should be manufactured as thin as the size andnumber of concavities and convexities will permit. -It is not essentialto lay down any rule for thickness orfor the size as the intensity willbe decreased by density, and that, therefore, the thickness will begoverned by the extent of surface required. Y y

In the making of dioptric lenses, sharpness at the anglesV of the zonesis -of the utmost importance, and to effect this important object it maybe found necessary to make the parts of the mold which are to form theangles of the zones with apertures (so small as to be nearly invisibleto the naked eye) for the escape of air from the cavity of the mold,otherwise atmospheric air may be confined in such cavities, and whenpressure is applied, the air thus confined will prevent the glass fromentering and assuming the required form of the sharp angles of the mold.

The holes should be very small and at such distances apart as to insurethe escape of the air.

When that part of the mold which forms the curved surfaces of the zonesis made in sections sutlicient space can be left between the differentzones for the escape of the air.

In the manufacture of the dioptric lens invented by me I use a metalmold or molds as I have already described, the reverse of the figure tobe produced and which will require accuracy in construction and finish.

The melted glass being prepared in the usual way well known to glassworkers, is to be put into the mold and the same process or labor isrequired in producing a lens, as is observed in molding by pressure anyother article from melted glass. The quality of the glass is notessential, but as light is always lost even in passing through the mosttransparent body, it will be more economical as well as more useful toemploy a good quality of glass and as white as possible, as white glasswill permit the more free passage of light, and with more brilliancythan an inferior quality and of less whiteness.

In describing my invention as a manufacture and its adaptation to thevarious uses hereinbefore mentioned it is not essential to detail thepeculiar way in which sea lights are used nor the adaptation of thedioptric lens to the several purposes spoken of other than sea lightsnor the many sided lanterns, whether stationary or revolving, in use,nor the peculiar shape of the case or shell, nor the lamp, nor the manyways in which light may be refracted as any person essaying to use ormanufacture my dioptric lens will beprepared with the necessary means,and I therefore consider it unnecessay to detail in words or to show in.the drawings the manner of constructing the different kinds ofapparatus in use for that glass in steps or rings by pressure inmetalpurpose, I therefore disclaim the inventiorfl lo molds,substantially as specified. of any apparatus connected With the use othe doptrc lens- JOHN L. GILLILAND. 5 What I claim as my invention anddesire Witnesses:

to secure by Letters Patent is- CANSTEN BROWN,

The manufacture of dioptric lenses of WM. H. BISHOP.

